The long-term goal of this project is to understand the role cadherins and catenins play in cell-cell adhesion, both as structural components of the adherens junction and as cellular signaling molecules. The components of he adherens junction have been shown to play an important role in maintenance of normal tissues. Mutations in the proteins that make up these junctions often result in tumor formation. In some cases, this is due to inability of the cells to form the physical structure, that is, the junction and in other cases it is due to alterations in signaling pathways. The cadherin, as the transmembrane components of the adherens junctions, have been linked to the wnt or wingless signaling pathway. The wnt pathway also includes APC which is often mutated in carcinomas, particularly in colon carcinomas. A complete picture of the protein- protein interactions involved in the components of this pathway will lead to a better understanding of how cells become tumorigenic and eventually to novel diagnostics and/or treatments for carcinomas. The specific aims of this proposal are focused on understanding some of the properties of cells that are changes during tumor formation and that are dependent upon the cadherin/catenin complex. Specifically, we propose to: 1. Establish a role for cadherins in cell motility. 2. Characterize structural and functional differences between beta-catenin and plakoglobin (gamma-catenin). 3. Examine alpha-catenin for additional binding proteins. To accomplish these goals, we will make use of molecular constructs, often made up of chimeric molecules. These constructs will be transfected into mammalian tissue culture cells to observe their effect on cellular behavior and phenotype. Protein-protein interactions will be determined by several means which include co-immunoprecipitation reactions, co- localization in tissue culture cells and yeast two hybrid analysis. Protein-protein interactions will also be analyzed by co-transfecting interaction domains of two proteins into eukaryotic cells followed by co- localization in intact cells (immunofluorescence) and co- immunoprecipitation of cell extracts.